Cylinder barrel inside surface treatment apparatus and method

ABSTRACT

A cylinder barrel inside surface treatment apparatus for providing a uniform treatment finish is disclosed. The treatment apparatus includes a pallet on which a cylinder block is placed with a gasket surface faced upward. A top opening of a cylinder barrel of the cylinder block is covered by a cover member having a concave portion communicating with the top opening. A nozzle having treatment solution spray holes is attached to the cover member. The treatment solution is sprayed toward a wall of the concave portion from the treatment solution spray holes and flows along the wall from a top end to a bottom end of the cylinder barrel inside surface.

FIELD OF THE INVENTION

The present invention relates to an improvement in a technique for causing a treatment solution to come into contact with an inside surface of a cylinder barrel of an engine and treating the cylinder barrel inside surface.

BACKGROUND OF THE INVENTION

An inside surface of a cylinder barrel of an engine is exposed to friction from a piston ring and high heat from combustion of fuel, thus requiring the surface to be strong. A surface treatment is effective for increasing the durability of the surface. With a plating treatment, which is one type of surface treatment, any surface fouling or the like is preferably removed prior to the plating treatment. The process of removing fouling substances before the surface treatment is referred to as pre-treatment.

An example of a plating pre-treatment will now be described with reference to FIG. 9 hereof.

As shown in FIG. 9, an etching treatment, an acid activation treatment, a first zincate conversion treatment, a dissolution activation treatment, and a second zincate conversion treatment are performed in the pre-treatment. The etching treatment alone is made up of a plurality of steps including chemical treatment using a treatment solution, primary and secondary rinses for cleaning, and an idler or the like to prevent drying. A specific example of the chemical treatment step as one of these steps is disclosed, e.g., in Japanese Patent Application Laid-Open Publication No. 2008-214730 (JP-A 2008-214730).

Reference is made next to FIG. 10 showing the chemical treatment apparatus disclosed in JP-A 2008-214730.

As shown in FIG. 10, a cylinder block 101 is mounted on a pallet 104 provided with a member 103 for closing off a bottom opening, and the bottom opening of the cylinder block 101 is closed off. The pallet 104 is disposed above a pan 105, and a lid 107 provided with a nozzle 106 is moved as indicated by the arrow (1) to close off the top opening of the cylinder block 101.

A treatment solution is fed to the nozzle 106 from a treatment solution feed channel 108 as indicated by arrow (2).

The supplied treatment solution is sprayed at the bottom portion of a cylinder barrel 110 from a treatment solution spray hole 109 as indicated by the arrow (3), and the treatment solution ascends while coming in contact with an inside surface of the cylinder barrel 110, as indicated by arrow (4).

The treatment solution in the cylinder barrel 110 is discharged mainly from a first drainage passage 111 provided to the pallet 104, as indicated by arrow (5), and the remainder of the treatment solution is discharged from a second drainage passage 112 provided to the lid 107, as indicated by arrow (6).

However, cylinder blocks are configured in a variety of ways. The inventors therefore applied the same etching treatment to a cylinder block configured without a crankcase part 102.

As shown in FIG. 11, a cylinder block 114 is mounted on a pallet 115 so that a gasket surface 113 is facing upward. A step portion 117 of the cylinder block 114 is sealed by a seal member 116. A top opening 119 of a cylinder barrel 118 is covered by a cover member 121 having a concave portion 120 leading to the top opening 119 of the cylinder barrel 118. A nozzle 122 for feeding treatment solution to the inside surface of the cylinder barrel 118 is provided to the cover member 121, and treatment solution spray holes 123 for spraying treatment solution are provided at the bottom of the nozzle 122.

The following results were obtained when the treatment solution was fed in the same manner as shown in FIG. 9 in the cylinder block 114. Reference characters A, B, and C in FIG. 11 indicate top, middle, and bottom measurement points, respectively, of the inside surface of the cylinder barrel 118.

When the high-temperature treatment solution is sprayed from treatment solution spray holes 123, 123, the treatment solution accumulates on the pallet 115 and ascends the inside of the cylinder barrel 118 to reach the concave portion 120. As a result, point C increases in temperature first, then point B, and lastly point A. Moreover, since heat retained by the treatment solution is absorbed by the cylinder barrel 118 before the treatment solution reaches point A, the temperature decreases. As a result, a temperature difference having a maximum T1 of as much as 25° C. occurs between the temperature increase curve of point A and the temperature increase curve of point C, as shown in FIG. 12.

The surface of the cylinder barrel is etched (corroded) by the treatment solution, but the amount of etching varies according to the temperature. A temperature difference having a maximum T1 of 25° C. is expected to affect the etching treatment. The amount of etching at each of the points A, B, and C was therefore examined.

As shown in FIG. 13A, the etching amount x1 was adequate at points B and C, but was low at point A.

When the etching amount is low, i.e., inadequate, adhesion of the plating is expected to decrease. The plating adhesion was therefore studied at each of the points A, B, and C.

When plating was applied to the pre-treated cylinder barrel, it was apparent that the peel width y1 of the plating was small at points B and C and large at point A, as shown in FIG. 13B. This is because a temperature difference on the inside surface of the cylinder barrel causes the treatment to be unevenly performed. Specifically, a technique is needed for treating the inside surface of a cylinder barrel, whereby the surface treatment can be made uniform.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a technique for treating the inside surface of a cylinder barrel, whereby the surface treatment can be made uniform.

According to an aspect of the present invention, there is provided a cylinder barrel inside surface treatment apparatus for causing a treatment solution to come into contact with an inside surface of a cylinder barrel provided to a cylinder block of an internal combustion engine and treating the cylinder barrel inside surface, which apparatus comprises: a pallet for supporting the cylinder block with a gasket surface of the cylinder block faced upward, and closing off a bottom opening of the cylinder barrel; a first drainage passage provided to the pallet for discharging a portion of the treatment solution accumulated in the cylinder barrel; a cover member placed on the gasket surface for covering a top opening of the cylinder barrel and having at a bottom thereof a concave portion communicating with the top opening of the cylinder barrel; a nozzle inserted from above downward into and attached to the cover member and having treatment solution spray holes for spraying the treatment solution toward a wall of the concave portion so as to feed the treatment solution to the inside surface of the cylinder barrel along the concave portion wall; and a second drainage passage provided in the cover member for discharging the remaining treatment solution accumulated in the cylinder barrel.

In the thus-arranged apparatus, since the treatment solution is sprayed in the concave portion rather than being sprayed directly onto the inside surface of the cylinder barrel, it is possible to prevent reaction that is biased toward the portion directly contacted by the treatment solution, so that the reaction can be made uniform. As a result, the inside surface of the cylinder barrel will be uniformly etched, allowing plating adhesion to be improved.

Preferably, the treatment solution spray holes are positioned upwardly of a top edge of the cylinder block. Since the treatment solution flows along the inside surface of the cylinder barrel from the top end to the bottom end thereof, the inside surface is uniformly etched.

Desirably, the pallet has on a top surface thereof a positioning pin adapted to be engaged in a hole formed in the cylinder block. The cylinder block is thereby always set on the pallet in a fixed position.

According to another aspect of the present invention, there is provided a cylinder barrel inside surface treatment method for causing a treatment solution to come into contact with an inside surface of a cylinder barrel provided to a cylinder block of an internal combustion engine and treating the cylinder barrel inside surface, which method comprises the steps of: placing the cylinder block, with a gasket surface thereof faced upward, on a pallet for closing off a bottom opening of the cylinder barrel; covering, while inserting a treatment solution feeding nozzle into a top opening of the cylinder barrel, the cylinder barrel top opening with a cover member having at a bottom thereof a concave portion communicating with the cylinder barrel top opening; spraying the treatment solution toward a wall of the concave portion from treatment solution spray holes provided to the nozzle so as to feed the treatment solution along the wall of the concave portion to the cylinder barrel inside surface; and discharging a portion of the treatment solution accumulated in the cylinder barrel from a first drainage passage provided to the pallet and discharging a remaining part of the treatment solution accumulated in the cylinder barrel from a second drainage passage provided to the cover member.

By introducing the treatment solution from above the cylinder barrel and causing the liquid surface to rise back from below to circulate the treatment solution, the difference in temperature between the top and the bottom of the inside surface of the cylinder barrel can be reduced, and the surface treatment can be made uniform. As a result, the inside surface of the cylinder barrel is uniformly etched, and plating adhesion can therefore be improved.

It is preferred that the treatment solution be fed from a top end to a bottom end of the inside surface of the cylinder barrel.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a side view showing an apparatus for treating an inside surface of a cylinder barrel, according to an embodiment of the present invention;

FIG. 2 is a sectional view showing a surface treatment unit of FIG. 1;

FIGS. 3A and 3B are cross-sectional views illustrative of a process for positioning a cylinder block;

FIGS. 4A to 4C are cross-sectional views illustrative of a process for treating the surface of the cylinder block;

FIG. 5 is a graph showing the change in temperature of the inside surface of the cylinder barrel of FIG. 2;

FIG. 6 is a graph showing for comparison the temperature differences of the inside surface of the cylinder barrel in the present embodiment and the prior art;

FIG. 7 is a graph showing an etching amount in the present embodiment;

FIG. 8 is a graph showing plating adhesion in the present embodiment;

FIG. 9 is a view showing a pre-treatment process in conventional plating;

FIG. 10 is a schematic view illustrating a conventional surface treatment apparatus;

FIG. 11 is a cross-sectional view showing the conventional surface treatment apparatus as used in a cylinder block having no crankcase part;

FIG. 12 is a graph showing changes in temperature of the inside surface of a cylinder barrel during conventional surface treatment; and

FIGS. 13A and 13B are graphs showing etching amounts and plating adhesion in the conventional surface treatment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, an apparatus 10 for treating an inside surface of a cylinder barrel according to the present embodiment is provided with a base 12 having adjusters 11; lower columns 13 provided upright on the base 12; a middle support member 15 provided on the top ends of the lower columns 13; a pan 16 for collecting a treatment solution, the pan 16 being supported by the middle support member 15; a treatment solution discharge tube 14 for leading the treatment solution collected in the pan 16 to the outside; an enclosure member 17 provided above the pan 16; a surface treatment unit 20 provided on the middle support member 15 and surrounded by the enclosure member 17; a drainage tube 21 for directing drainage from the top portion of the surface treatment unit 20, the drainage tube 21 being provided to the surface treatment unit 20; a treatment solution detector 22 for monitoring the drainage tube 21; middle columns 23 provided upright on the middle support member 15; an upper support member 24 provided on the top ends of the middle columns 23; upper columns 25 provided upright on the upper support member 24; and a top panel 26 provided on the top ends of the upper columns 25.

The surface treatment unit 20, which shall be described in detail hereinafter, is provided with a pallet 31 for supporting a cylinder block 27 subjected to a surface treatment; a cover member 32 for covering a top portion of the cylinder block 27; and a second drainage passage 33 provided to the cover member 32 so as to discharge a portion of the treatment solution.

The surface treatment apparatus 10 for the inside surface of a cylinder barrel is also provided with a raising/lowering cylinder 35 for raising and lowering the cover member 32 via a raising/lowering rod 34, the raising/lowering cylinder 35 being provided to the top panel 26; a pivoting part 37 provided so as to be able to pivot about a rotary shaft 36 at a bottom end of the raising/lowering rod 34; and a pivot cylinder 41 for causing the pivoting part 37 to pivot via an advancing/retreating rod 38, the pivot cylinder 41 being provided to the lower portion of the raising/lowering rod 34.

The relevant parts of the surface treatment apparatus 10 for the inside surface of a cylinder barrel will next be described.

As shown in FIG. 2, the surface treatment unit 20 is composed of a pallet 31 for supporting the cylinder block 27 so that a gasket surface 42 of the cylinder block 27 faces upward, and closing off a bottom opening 44 of a cylinder barrel 43; a first drainage passage 45 provided to the pallet 31 so as to discharge a portion of the treatment solution accumulated in the cylinder barrel 43; a step portion seal member 47 provided to the pallet 31 so as to seal a step portion 46 of the cylinder block 27; a positioning pin 51 provided to the pallet 31 so as to position a hole 48 of the cylinder block 27; a cover member 32 mounted on the gasket surface 42 so as to cover a top opening 52 of the cylinder barrel 43, the cover member 32 having a concave portion 53 leading to the top opening 52 of the cylinder barrel 43; a gasket surface seal member 54 provided to a bottom end of the cover member 32 so as to seal the gasket surface 42; a nozzle 57 for feeding treatment solution to the inside surface of the cylinder barrel 43 along a wall 55 of the concave portion 53, the nozzle 57 being inserted downward from the top of the cover member 32 and attached to the cover member 32, and having treatment solution spray holes 56 for spraying the treatment solution toward the wall 55 of the concave portion 53; a treatment solution feed channel 58 for feeding the treatment solution to the nozzle 57; and the second drainage passage 33 provided to the cover member 32 so as to discharge the remaining treatment solution accumulated in the cylinder barrel 43.

The treatment solution spray holes 56 formed in the nozzle 57 are positioned higher than the top opening 52 of the cylinder block 27. The treatment solution therefore flows uniformly from the top end of the inside surface of the cylinder barrel 43 to the bottom end thereof. The treatment solution spray holes 56 are composed of a plurality of holes, and are preferably in a radial arrangement in the radial direction of the nozzle 57 from the treatment solution feed channel 58, but may also be in a cross arrangement.

An operation of the surface treatment apparatus 10 described above will next be described based on FIGS. 3A through 4C.

FIGS. 3A and 3B show the process of positioning the cylinder block 27 in the surface treatment apparatus 10.

FIG. 3A shows the process of mounting the cylinder block 27 on the pallet 31. The cylinder block 27 is mounted on the pallet 31 as indicated by the arrow (7) so that the gasket surface 42 of the cylinder block 27 faces upward, the pallet 31 closing off the bottom opening 44 of the cylinder barrel 43. The positioning pin 51 is inserted in the hole 48, and the cylinder block 27 is thereby properly positioned on the pallet 31 at all times.

FIG. 3B shows the process of covering the top opening 52 of the cylinder block 27. The cover member 32 is moved as indicated by the arrow (8), and covers the top opening 52 of the cylinder barrel 43 while the nozzle 57 is inserted in the top opening 52 of the cylinder barrel 43.

FIG. 4A shows the process of feeding treatment solution to the nozzle 57. The treatment solution is fed to the nozzle 57 via the treatment solution feed channel 58, as indicated by the arrow (9). The treatment solution fed to the nozzle 57 sprays toward the wall 55 of the concave portion 53 from the treatment solution spray holes 56. The treatment solution is fed to the inside surface of the cylinder barrel 43 along the wall 55 of the concave portion 53, as indicated by the arrows (10).

FIG. 4B shows the process whereby the treatment solution is discharged from the first drainage passage 45. A portion of the treatment solution accumulated in the cylinder barrel 43 is discharged from the first drainage passage 45, as indicated by the arrow (11). The amount of treatment solution fed is greater than the amount discharged from the first drainage passage 45. The treatment solution therefore accumulates in the cylinder barrel 43, as indicated by the arrows (12). The nozzle 57 extends downward past the cylinder barrel 43, and the volume of the space formed by the inside surface of the cylinder barrel 43 and the outside surface of the nozzle 57 is thereby reduced. The ascent of the treatment solution is therefore accelerated, and the number of steps involved in the treatment can be reduced.

FIG. 4C shows the process whereby the treatment solution is discharged from the second drainage passage 33. The remainder of the treatment solution accumulated in the cylinder barrel 43 is discharged from the second drainage passage 33, as indicated by the arrow (13). Monitoring the drainage through the use of the treatment solution detector 22 (FIG. 1) enables the surface treatment to be reliably performed.

The inventors investigated the change in temperature at points A, B, and C shown in FIG. 2, and the obtained results will be described using FIG. 5.

As shown in FIG. 5, the temperature immediately increased when the high-temperature treatment solution was fed at points B and C in the middle and lower portions of the cylinder barrel 43. The results also showed that the temperature increase was also rapid at the upper point A as compared with the prior art example shown in FIG. 12. This is because the retained heat of the treatment solution is transferred first to point A by the high-temperature treatment solution being fed from above the inside surface of the cylinder barrel 43, and the first temperature increase thus occurs at point A. The reference symbol T2 refers to the maximum temperature difference.

The temperature difference in the present embodiment shown in FIG. 2 and the temperature difference in the prior art example shown in FIG. 10 were then compared. The results of this comparison are described using FIG. 6.

As shown in FIG. 6, the maximum temperature difference T1 in the prior art example was 25° C., whereas the maximum temperature difference T2 in the present embodiment was 12° C. At the time immediately after the feeding of the treatment solution started, the temperature difference between different positions on the inside surface of the cylinder barrel in the present embodiment was 15° C. or less; i.e., small. It is apparent that the temperature of the inside surface of the cylinder barrel is more uniform in the present embodiment than in the prior art example.

Reducing the temperature difference to 15° C. or less is also expected to minimize any effect on the etching treatment. The amount of etching at each of the points A, B, and C was therefore examined. The results are described using FIG. 7.

As shown in FIG. 7, the etching amount x2 was 2.5 μm or more at all of points A, B, and C; and was adequate. The plating adhesion was expected to improve when the etching amount was adequate. The plating adhesion at each of the points A, B, and C was therefore examined. The results are described using FIG. 8.

As shown in FIG. 8, when the pre-treated cylinder barrel was plated, the peel width y2 of the plating was small at all of the points A, B, and C. This indicates that the absence of large temperature differences on the inside surface of the cylinder barrel allows the treatment to be evenly performed.

An example was described in the embodiment in which the technique for treating a cylinder barrel surface according to the present invention was applied to pre-treatment for plating, but a pre-treatment for plating is not given by way of limitation; the invention may be applied to another surface treatment process provided that the surface treatment is performed on an inside surface of a cylinder barrel.

The technique for treating an inside surface of a cylinder barrel according to the present invention can be used in a plating pre-treating of an inside surface of a cylinder barrel.

Obviously, various minor changes and modifications of the present invention are possible in light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. 

1. A cylinder barrel inside surface treatment apparatus for causing a treatment solution to come into contact with an inside surface of a cylinder barrel provided to a cylinder block of an internal combustion engine and treating the cylinder barrel inside surface, the apparatus comprising: a pallet for supporting the cylinder block with a gasket surface of the cylinder block faced upward, and closing off a bottom opening of the cylinder barrel; a first drainage passage provided to the pallet for discharging a portion of the treatment solution accumulated in the cylinder barrel; a cover member placed on the gasket surface for covering a top opening of the cylinder barrel and having at a bottom thereof a concave portion communicating with the top opening of the cylinder barrel; a nozzle inserted from above downward into and attached to the cover member and having treatment solution spray holes for spraying the treatment solution toward a wall of the concave portion so as to feed the treatment solution to the inside surface of the cylinder barrel along the concave portion wall; and a second drainage passage provided in the cover member for discharging the remaining treatment solution accumulated in the cylinder barrel.
 2. The treatment apparatus of claim 1, wherein the treatment solution spray holes are positioned upwardly of a top edge of the cylinder block.
 3. The treatment apparatus of claim 1, wherein the pallet has on a top surface thereof a positioning pin designed to be engaged in a hole formed in the cylinder block.
 4. A cylinder barrel inside surface treatment method for causing a treatment solution to come into contact with an inside surface of a cylinder barrel provided to a cylinder block of an internal combustion engine and treating the cylinder barrel inside surface, the method comprising the steps of: placing the cylinder block, with a gasket surface thereof faced upward, on a pallet for closing off a bottom opening of the cylinder barrel; covering, while inserting a treatment solution feeding nozzle into a top opening of the cylinder barrel, the cylinder barrel top opening with a cover member having at a bottom thereof a concave portion communicating with the cylinder barrel top opening; spraying the treatment solution toward a wall of the concave portion from treatment solution spray holes provided to the nozzle so as to feed the treatment solution along the wall of the concave portion to the cylinder barrel inside surface; and discharging a portion of the treatment solution accumulated in the cylinder barrel from a first drainage passage provided to the pallet and discharging a remaining part of the treatment solution accumulated in the cylinder barrel from a second drainage passage provided to the cover member.
 5. The treatment method of claim 4, wherein the treatment solution is fed from a top end to a bottom end of the inside surface of the cylinder barrel. 